Bicycle driving mechanism.



No; 703,6I3. 4 Patented July I, I902.

T. C. ROBINSON;

BICYCLE DRIVING MECHANISM.

(Application flhd Dec. 98, 1899) (No Model.)

UNITED STATES PATENT OFFICE.

THOMAS C. ROBINSON, OF BOSTON, MASSACHUSETTS, ASSIGNOR OF ONE- HALF TOE. BAKER W'ELOH H. AUGUSTA WELOH, OF CAMBRIDGE,

MASSACHUSETTS.

BICYCLE DRIVING M ECHANISM.

SPECIFICATION forming part of Letters Patent No. 703,613, dated. July 1,1902.

Application filed December 26, 1899- Serial No- 741,587. (No model.)

T0 at whom it mag concern..-

of Boston, in the county of Suffolk and State of Massachusetts, haveinvented certain new and useful Improvements in Bicycle DrivingMechanism, of which the following is a specification.

This invention relates to bicycle driving mechanisms of that class inwhich the pedal is guided eccentrically to the driving-shaft for thepurpose of obtaining an increased leverage on the downstroke of thefoot. It is common in such mechanisms to employ a pedal-lever orequivalent carrying the pedal and guided eccentrically to thedriving-shaft and a compensating connection between the pedal-lever andthe crank. Heretofore this connection has been a sliding one, and theobjections to it' are a degree of complexity, considerable workingfriction, and exposure to dust.

The object of my invention is to overcome these. objections by providinga pivotal link connection between the pedal or pedal-lever and thecrank.

The invention consists in the novel features of construction andarrangement which I shall now proceed to describe and claim.

Of the accompanying drawings, Figure 1 represents a side elevation of abicycle driving mechanism constructed in accordance with my invention.Fig. 2 represents a plan view thereof with the bicycle-frame in section.Fig. 3 represents a view similar to Fig. 1, showing a modification.

Referring to the drawings, l designates the frame of a bicycle orsimilar vehicle, and 2' designates the driving-shaft or crank-shaft journaled in bearings on said frame. To said driving-shaft is affixed acrank 3.

4 is an eccentric having its inner part affixed by suitable means to theframe 1 and having a strap 5, adapted to revolve uponsaid inner part,suitable antifriction-bearings being interposed between the strap andthe fixed part. 1

6 is an arm or extension on the eccentricstrap 5, carrying the pedal 7at its outer end. The center of the eccentric 1 is placed a certaindistance in advance of the center of the driving-shaft 2, so that thepedal 7 travels in the pedal arm or lever 6.

'tween thev pedal and the driving-shaft.

. a circle eccentric to the driving-shaft, the Be it known that I,THOMAS C. ROBINSON,

greatest distance of the pedal from the shaft being reached when thepedal is at a point in its downward stroke.

8 is a link pivotallyconnected at the point 9 with the crank 3 and atthe point 10 with This link completes a positive connection between thepedal 7 and the driving-shaft 2.

The described driving mechanism is repeated on the opposite side of thebicycle. It

is apparent that, the riders foot pressing on the pedal 7willexert amaximum leverage on the driving-shaft 2 when the said pedal is at itsgreatest distance from said driving-shaft and a minimum leverage when itis at its least distance from said shaft. During different portions ofthe revolution of the pedal and crank-shaft the angle between thecrankshaft 3 and the link 8 will vary, being greatest when the pedal isfarthest from the driving-shaft and least when the pedal is nearest tosaid shaft, as seen in Fig. 1.

In the modification illustrated in Fig. 3 the link 8 instead of beingpivoted to the pedalarm 6 is pivoted to a lug 11 on the eccentricstrap,located at a point diametrically opposite the pedal-arm. In this casethe angle between the link and crank is greatest on the upstroke of thepedal and least on the downstroke.

It will be noted that there are in this mechanism no sliding joints inthe connection be- The joints 9 'and 10 are pivotal joints capable ofbeing constructed in a dust-proof manner and of operating with a verysmall amount of fric tion. The mechanism is exceedingly simple andstrong.

The mechanism shown in Fig. 3 has an advantage over that shown in Fig.1, due to the fact that the compensating connection between the pedaland the crank is made at a point on the opposite side of the center ofthe pedal-shaft from the pedal. The velocity of the pedal is thengreatest on the downstroke and least on the upstroke,.which is obviouslyan advantage, whereas in the arrangement shown in Fig. 1 the reverse istrue. The principal advantage is that with this form the pedal makes theupstroke with a diminishing bination of a frame, a driving-shaftjournaled thereon, a crank attached to said shaft, an eccentric affixedto said frame and having a strap, a pedal attached to said strap, and alink pivotally attached to the crank, and to the eccentric-strap at apoint on the opposite side of the center of the eccentric from saidpedal, whereby the upstroke velocity of the pedal is diminished.

In testimony whereof I have aflixed my sig- 2 5 nature in presence oftwo witnesses.

THOMAS C. ROBINSON. Witnesses:

C. F. BROWN, P. W. PEZZETTI.

